Dissertations / Theses on the topic 'Hierarchy routing'

A Mobile Ad hoc Network (MANET) is a collection of wireless mobile nodes forming a temporary network without the need for base stations or any other pre–existing network infrastructure. In a peer-to-peer fashion, mobile nodes can communicate with each other by using wireless multihop communication. Due to its low cost, high flexibility, fast network establishment and self-reconfiguration, ad hoc networking has received much interest during the last ten years. However, without a fixed infrastructure, frequent path changes cause significant numbers of routing packets to discover new paths, leading to increased network congestion and transmission latency over fixed networks. Many on-demand routing protocols have been developed by using various routing mobility metrics to choose the most reliable routes, while dealing with the primary obstacle caused by node mobility. ¶ In the first part, we have developed an analysis framework for mobility metrics in random mobility model. Unlike previous research, where the mobility metrics were mostly studied by simulations, we derive the analytical expressions of mobility metrics, including link persistence, link duration, link availability, link residual time, link change rate and their path equivalents. We also show relationships between the different metrics, where they exist. Such exact expressions constitute precise mathematical relationships between network connectivity and node mobility. ¶ We further validate our analysis framework in Random Walk Mobility model (RWMM). Regarding constant or random variable node velocity, we construct the transition matrix of Markov Chain Model through the analysis of the PDF of node separation after one epoch. In addition, we present intuitive and simple expressions for the link residual time and link duration, for the RWMM, which relate them directly to the ratio between transmission range and node speed. We also illustrate the relationship between link change rate and link duration. Finally, simulation results for all mentioned mobility metrics are reported which match well the proposed analytical framework. ¶ In the second part, we investigate the mobility metric applications on caching strategies and hierarchy routing algorithm. When on-demand routing employed, stale route cache information and frequent new-route discovery in processes in MANETs generate considerable routing delay and overhead. This thesis proposes a practical route caching strategy to minimize routing delay and/or overhead by setting route cache timeout to a mobility metric, the expected path residual time. The strategy is independent of network traffic load and adapts to various non-identical link duration distributions, so it is feasible to implement in a real-time route caching scheme. Calculated results show that the routing delay achieved by the route caching scheme is only marginally more than the theoretically determined minimum. Simulation in NS-2 demonstrates that the end-to-end delay from DSR routing can be remarkably reduced by our caching scheme. By using overhead analysis model, we demonstrate that the minimum routing overhead can be achieved by increasing timeout to around twice the expected path residual time, without significant increase in routing delay. ¶ Apart from route cache, this thesis also addresses link cache strategy which has the potential to utilize route information more efficiently than a route cache scheme. Unlike some previous link cache schemes delete links at some fixed time after they enter the cache, we proposes using either the expected path duration or the link residual time as the link cache timeout. Simulation results in NS-2 show that both of the proposed link caching schemes can improve network performance in the DSR by reducing dropped data packets, latency and routing overhead, with the link residual time scheme out-performing the path duration scheme. ¶ To deal with large-scale MANETs, this thesis presents an adaptive k-hop clustering algorithm (AdpKHop), which selects clusterhead (CH) by our CH selection metrics. The proposed CH selection criteria enable that the chosen CHs are closer to the cluster centroid and more stable than other cluster members with respect to node mobility. By using merging threshold which is based on the CH selection metric, 1-hop clusters can merge to k-hop clusters, where the size of each k-hop cluster adapts to the node mobility of the chosen CH. Moreover, we propose a routing overhead analysis model for k-hop clustering algorithm, which is determined by a range of network parameters, such as link change rate (related to node mobility), node degree and cluster density. Through the overhead analysis, we show that an optimal k-hop cluster density does exist, which is independent of node mobility. Therefore, the corresponding optimal cluster merging threshold can be employed to efficiently organise k-hop clusters to achieve minimum routing overhead, which is highly desirable in large-scale networks. ¶ The work presented in this thesis provides a sound basis for future research on mobility analysis for mobile ad hoc networks, in aspects such as mobility metrics, caching strategies and k-hop clustering routing protocols.

Ce memoire traite de la conception assistee par ordinateur dans le domaine des circuits electroniques a haut niveau d'integration, en presentant une methode de conception pour ces circuits, et la chaine d'outils logiciels adaptes a cette methode. La premiere partie critique deux methodologies de conception typiques dans ce domaine. La seconde partie decrit les differentes phases de la methodologie s'inscrivant dans le cadre de la norme edif. La troisieme partie presente plusieurs outils de cao developpes au cours de l'etude, a savoir: une chaine complete d'edition; une chaine complete de verification; un routeur de canal; un routeur global; des post-processeurs de traduction et de visualisation

This thesis is focused on structure of future IPv6 routing tables. It contains basic information about IPv6 addresses , description of hierarchy address allocation, multihoming , strategy of IPv4/IPv6 address allocation, statistics of structure properties at routing tables and forecast of future space for address IPv6 protocol. Other part of this thesis is implementation of IPv6 address generator which generates addresses according given configuration. This thesis simultaneously includes investigation of strategy IPv6 address allocation at region of RIPE NCC organization.

Healthcare is generally characterized by deep traditions, old working methods, and clear hierarchies. A central part of medical wards is the so-called “round”. During the round, physicians and nurses visit the patients and decide on further action. The round is a central process at wards and affect the rest of the working day, both for physicians and nurses. In this study, the round process was observed at Ward 4 at Norrtälje Hospital. The staff at Ward 4 experienced high-stress levels and this was related to an ineffective round according to a prestudy conducted by Clinical Innovation Fellowships. The project aimed at producing a new optimized round routine that would reduce the high-stress levels. The study was conducted through observations, dialogue with staff, interviews, surveys, comparative observations at other wards at Norrtälje Hospital and other hospitals as well as theoretical studies. The main difficulties discovered in our study with the round process at Norrtälje Hospital were that (i) information was communicated dual, (ii) the round process was too time-consuming, (iii) late decision-making, (iv) inefficient role for nurses and the (v) priority of work. The study resulted in a recommendation of a new round routine in which we have taken the staff’s interests into account as well as literature and research within the field of how developing healthcare processes. Our target was to increase communication and collaboration between physicians and nurses and furthermore exploiting human resources in the best possible way. Our main recommendation was to introduce a seated pre-round prior to commencing the daily round routine and to introduce a reconciliation meeting afterwards.
Sjukvård är generellt sett präglat av inrotade traditioner, gamla arbetsmetoder och tydliga hierarkier. En central del på medicinska avdelningar är den så kallade ronden. Under ronden besöker läkare och sköterskor patienterna och beslutar om vidare åtgärder. Arbetet under ronden påverkar sedan resten av arbetsdagen, både för läkare och sköterskor, eftersom den är en väldigt central del av arbetsdagen på en medicinavdelning. I denna studien så undersöktes rondprocessen på avdelning 4 på Norrtälje Sjukhus. Bakgrunden till detta var att personalen präglats av höga stressnivåer och att det varit ett resultat av en ineffektiv rond. Detta framkom från en förstudie utförd av Clinical Innovation Fellowships. Vår studie syftade i att producera en ny effektivare rondrutin som i sin tur skulle minska stressen hos personalen. Detta genomfördes med hjälp av observationer, dialog med personal, intervjuer, enkätundersökningar, jämförande observationer på andra avdelningar och andra sjukhus, och teoristudier. Dom största problemen som upptäcktes i vår studie var att (i) information kommuniceras dubbelt, (ii) ronden tog för lång tid, (iii) att beslut inte fattas tillräckligt fort, (iv) sköterskans roll under ronden och (v) prioritering av patienter. Studien resulterade i ett förslag till en ny rondrutin som strävar efter att öka kommunikation och samarbete mellan läkare och sköterskor, och samtidigt utnyttja personalresurser på ett optimalt sätt. Vår främsta rekommendation var att införa en sittrond före gåronden och avsluta med ett avstämningsmöte.

碩士
淡江大學
電機工程學系碩士在職專班
98
In this paper, we present Bidirectional Hierarchy-based Anycast Routing (BHAR), a routing protocol for collecting data over multi-hop. In comparative to HAR, BHAR speeds up and improve the mechanism to construct hierarchical trees and to repair the route. In BHAR, sinks and sources can initial to construct a hierarchical tree. By knowing only its own parent and neighbor, each node in BHAR can join a tree; a tree can learn the routes to a remote sink by exchanging its routes with its neighboring trees, and send data to the nearest sink by intermediate trees; each node can perform route repair without geographical information or being controlled remotely, and perform local network topology optimization simultaneously in order to prevent the impact to the network and to data communication by periodically and conditionally network reconstruction. We evaluate the performance of BHAR by using VC++ and comparing with those of HAR. The simulation results demonstrate that the average waiting time for a node to join a tree decrease when the number of sinks and sources increase in BHAR. The impact of the increase of the node number and network size to the performance of BHAR is relatively small, which means the scalability is much better. BHAR can endure more nodes to be failed and maintain effective routing operation, which has improve the robustness of BHAR. BHAR achieves much higher performance on route repair in the situation of the unevenly distribution due to different factors.

碩士
國立政治大學
資訊科學學系
99
In Delay Tolerant Networks (DTNs), there is no guarantee that a stable connected path between source and destination nodes always exists because of high node mobility. The current DTN routing protocols can be summarized into three categories: opportunistic, prediction-based and scheduling protocols. However, these routing protocols have some deficiencies and are not specifically focused on the urban areas which have primarily two hierarchical nodes, namely pedestrian and bus nodes. We proposed a Hybrid Hierarchy Routing Protocol, a bus-based architecture for urban areas. We established the rules of data transmission when one node contacts other nodes. More specifically, Ped-to-Ped, Ped-to-Bus and Bus-to-Bus contacts, have different judgments and restrictions for data forwarding. The simulation results demonstrate that the Hybrid Hierarchy Routing Protocol can effectively reduce the delivery delay and improve the successful delivery rate. And in given certain speed and buffer sizes, our algorithm has the most prominent performance.

碩士
國立中正大學
資訊工程研究所
107
Compared with traditional networks, the rise of Software Defined Network (SDN) technology helps us manage network traffic more flexibly and better, and control the quality of service (QoS) more efficiently. In the traditional network, the shortest path or single path is used for transmission, and the load condition and other QoS restrictions on the path are not considered. Therefore, this paper proposes a multi-path transmission mechanism with multiple QoS orientation based on the software-defined network environment. The software-defined network monitors multiple QoS metrics in time and performs weight analysis by hierarchical analysis to set the link cost, and then finds multiple low-cost paths to transmit network traffic.

A Mobile Ad hoc Network (MANET) is a collection of wireless mobile nodes forming a temporary network without the need for base stations or any other pre–existing network infrastructure. In a peer-to-peer fashion, mobile nodes can communicate with each other by using wireless multihop communication. Due to its low cost, high flexibility, fast network establishment and self-reconfiguration, ad hoc networking has received much interest during the last ten years. However, without a fixed infrastructure, frequent path changes cause significant numbers of routing packets to discover new paths, leading to increased network congestion and transmission latency over fixed networks. Many on-demand routing protocols have been developed by using various routing mobility metrics to choose the most reliable routes, while dealing with the primary obstacle caused by node mobility. ¶ In the first part, we have developed an analysis framework for mobility metrics in random mobility model. ... ¶ In the second part, we investigate the mobility metric applications on caching strategies and hierarchy routing algorithm. ...